Conventional airflow models for use in computer control of vehicular engines suffer from the fact that gas densities and volumetric efficiencies used in control algorithms are not constant, thereby requiring use of complex error correction factors. Such correction factors, in turn, are highly dependent on hard-to-achieve precise measurements of engine operating parameters, such as manifold absolute pressure. Additionally, prior approaches require complex combinations of software tabular and surface data to properly calibrate the controller to estimate normally unmeasured parameters, such as cylinder temperature.
The complexity of cylinder temperature calibration requires large amounts of time in specialty dynamometer cells generating huge data sets for calibration and verification. Advanced engine systems utilize devices which affect exhaust gas residual content in a selected cylinder at the completion of an intake stroke. These devices typically include variable valve timing devices or manifold tuning valves and all require complex modifiers to parameters such as volumetric efficiency to obtain acceptably useful calibration.
Hence, there is a need for an improved model approach to modeling volumetric efficiency and gas density for use in controlling operating conditions of a vehicle engine.